User reported searching "Maduk - Leave A Light On" on Tidal silently
downloaded Tom Walker's completely different song of the same name, then
embedded Maduk's metadata into Tom Walker's audio. Three layers of
defense all failed permissively. Two of them are fixed here; the third
(score formula weights) was left alone since these two together cover it.
Layer 1 fix — candidate artist gate (web_server.py:27782)
Old: `if _best_artist < 0.4 and confidence < 0.85: continue`
New: `if _best_artist < 0.5 and confidence < 0.85: continue`
SequenceMatcher returns exactly 0.400 for "maduk" vs "tom walker"
(5-char vs 10-char strings with coincidental char matches), which
slipped past the strict `< 0.4` check. The word-boundary containment
check earlier in the function already short-circuits legitimate
formatting variations to sim=1.0, so falling to SequenceMatcher means
strings are genuinely different. 0.5 closes the fencepost AND gives
a small safety buffer.
Layer 3 fix — AcoustID verification (acoustid_verification.py:316)
When title matches but artist doesn't AND expected artist isn't found
anywhere in AcoustID's returned recordings:
Old: always SKIP (let file through, assume cover/collab)
New: FAIL if artist_sim < 0.3 (clear mismatch)
SKIP if artist_sim >= 0.3 (ambiguous — cover/collab/formatting)
The 0.3 cutoff catches hard mismatches like Maduk/Tom Walker (sim ~0.2)
while preserving benefit-of-the-doubt for borderline artist formatting
differences. Legitimate covers and collabs where the expected artist
appears anywhere in AcoustID's recordings still PASS via the existing
secondary-match loop above.
Both fixes are defense-in-depth — either alone would have caught this
bug. Together they close the pre-download AND post-download gaps.
All 292 tests pass. Version bumped to 2.39 with changelog entries.
8f85b0c251